Similar observations were made for non-toxigenic strains  showing that also pharyngeal
Detroit 562 cells can be invaded by C. diphtheriae and that viable intracellular bacteria can be detected up to 48 h after infection. While host cell receptors and invasion-associated proteins of the pathogen are still unknown, bacterial adhesion factors have been recently at least partially characterized on the molecular level. BVD-523 manufacturer C. diphtheriae strain NCTC13129 is able to assemble three distinct types of pili on its surface [11, 12]. Mutant analyses showed that the SpaA-type pilus is sufficient for adhesion of this strain to pharynx cells, shaft proteins are not crucial for pathogen-host interaction, and adherence to pharyngeal cells is greatly diminished when minor pili proteins SpaB and SpaC are lacking . The results obtained in other studies indicated the existence of additional proteins besides pili subunits selleck products involved in adhesion buy GSK2879552 to larynx, pharynx, and lung epithelial cells, since a total loss of attachment to pharyngeal cells due to mutagenesis of pili- and sortase-encoding genes could not be observed and attachment to lung or larynx cells was less affected by the mutations. This is in line with a number of studies suggesting the multifactorial mechanism of adhesion (reviewed in ). Furthermore, Hirata and co-workers [7, 15] described three distinct patterns of adherence to HEp-2 cells, an aggregative, a
localized, and a diffuse form, an observation that hints also to the existence of several adhesion factors and different receptors on the host cell surface. The involvement of different C. diphtheriae proteins to adherence to
distinct cell types is further supported by work on adhesion to human erythrocytes, showing that non-fimbrial surface proteins 67p and 72p, which were up to now only characterized by their apparent mass, are involved in this process . Interestingly, besides strain-specific differences in adherences (see references cited above), Beta adrenergic receptor kinase also growth-dependent effects were observed. In a study using two toxigenic C. diphtheriae strains and erythrocytes as well as HEp-2 cells, de Oliveira Moreira and co-workers  showed an effect of iron supply on hemagglutination and lectin binding properties of the microorganisms. In this study, we present a characterization of different non-toxigenic C. diphtheriae and a toxin-producing strain with respect to adhesion to and internalization into epithelial cells. Analyses reveal significant strain-specific differences in host colonization and macromolecular surface structures of the studied strains, while neither of the strains evoked rapid cell damage under the conditions tested. Results Adhesion of C. diphtheriae to epithelial cells, invasion of host cells and intracellular survival In this study, adhesion of six non-toxigenic strains and one toxin-producing C. diphtheriae to Detroit562 cells was analyzed (Fig. 1).